A carbon-fiber-reinforced plastic comprising carbon fibers and a matrix resin (hereinafter, also referred to as a “CFRP”) is developed broadly in various uses because it is excellent in mechanical properties, light-weight property, corrosion resistance and the like. As a process of producing a CFRP, although there is a process using a so-called “prepreg” which is impregnated with a resin in advance, in a case where it is required to broaden the range of the moldable shape of CFRP and shorten the time required for molding, for example, in a case where a mass production is required such as in parts for vehicles or parts for electronic equipment, a process is frequently employed wherein a carbon fiber base material (dry-type carbon fiber base material) substantially containing no resin is formed in a predetermined shape, and by impregnating a matrix resin thereinto, a desired CFRP is molded.
In such a process of molding a CFRP by impregnating a matrix resin into a dry-type carbon fiber base material, in a case of a CFRP molded using a base material formed by using continuous carbon fibers, although the mechanical properties are excellent, because the continuous carbon fibers are hard to move at the steps of shape forming and molding, the moldability (shape formability) into a desired shape is poor. On the other hand, in a case of a CFRP molded using a base material formed by using discontinuous carbon fibers, although the moldability (shape formability) is excellent because the carbon fibers can easily move, only low mechanical properties can be achieved.
Further, in a case of a so-called “unidirectional” (UD) prepreg or a UD tape obtained by arranging continuous carbon fibers in one direction because the mechanical properties in the direction oriented with the carbon fibers are very high, by disposing the carbon fiber base material in a direction applied with a load when a CFRP product is designed, a product having desired mechanical properties in a specified direction can be made with a lower amount of material. However, in a case of a CFRP using a base material composed of discontinuous carbon fibers to obtain excellent moldability (shape formability), a CFRP provided with such a high anisotropy to mechanical properties has not existed to date. Thus, it has been difficult to obtain a material satisfying both of shape formability and mechanical properties in a specified direction.
Although CFRPs using base materials composed of discontinuous carbon fibers are disclosed in JP-A-2010-235779, JP-A-2010-37358, JP-A-2002-212311, JP-A-2004-43985 and the like, all of these aim to achieve a good isotropy with respect to mechanical properties, and there is no description as to a technical concept of intentionally providing a high anisotropy. In particular, there is not any suggestion as to a technical concept of intentionally providing a high anisotropy at a stage of a carbon fiber base material which is not yet impregnated with a resin. Further, although JP-A-2010-229238 mentions with respect to anisotropy (a flexural elastic modulus in a specified direction is 2,500 GPa or more), it does not mention the degree of anisotropy (orientation degree).
Accordingly, it could be helpful to provide a carbon-fiber-reinforced plastic capable of realizing achievement of excellent mechanical properties in a desired direction with a small amount of carbon fibers by imparting an anisotropy in a specified range particularly at a stage of a carbon fiber base material before resin impregnation while utilizing good shape formability and moldability in a case of using a base material composed of discontinuous carbon fibers, and a process of producing the same.